Send 0.95 from TOF controller if there is no cone.

This lets us detect cone presence separately from unplugged sensor.

Change-Id: I0f70c1229bd88b5c50ed2fdf043361d072c41402
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/frc971/wpilib/dma_edge_counting.cc b/frc971/wpilib/dma_edge_counting.cc
index ba8fdf4..4e8a158 100644
--- a/frc971/wpilib/dma_edge_counting.cc
+++ b/frc971/wpilib/dma_edge_counting.cc
@@ -28,11 +28,11 @@
   if (have_prev_sample_ && high_time_ != 0 && prev_sample_.Get(input_) &&
       !sample.Get(input_)) {
     last_width_ = (sample.GetTime() - high_time_) * 1e-6;
-    high_time_ = 0;
     poll_count_ = 0;
   } else if (have_prev_sample_ && !prev_sample_.Get(input_) &&
              sample.Get(input_)) {
-    high_time_ = prev_sample_.GetTime();
+    last_period_ = (sample.GetTime() - high_time_) * 1e-6;
+    high_time_ = sample.GetTime();
     poll_count_ = 0;
   }
   have_prev_sample_ = true;
@@ -46,6 +46,7 @@
     high_time_ = 0;
     have_prev_sample_ = false;
     last_width_ = ::std::numeric_limits<double>::quiet_NaN();
+    last_period_ = ::std::numeric_limits<double>::quiet_NaN();
   }
   poll_count_++;
 }